Robert Carroll served four months of a 14-month prison sentence for misconduct in a public office (Picture: MEN)

A former undercover cop claims that during a police training exercise, along with colleagues, he was encouraged to inhale heroin smoke.

Robert Carroll, 41, has further stated that this experiment led him deep into heroin, alcohol and substance addiction.

The former constable has launched a civil case against Greater Manchester Police (GMP) due to this alleged event at the Sedgley Park training complex in 2008.

Carroll said of the experience: ‘I felt ill when I walked out of there, they encouraged us to smell the smoke.

‘That was pretty much the start of my downfall. Ultimately, I had a breakdown.’

He had worked undercover with heroin drug dealers where he claimed he was forced to smuggle narcotics in his mouth and sometimes swallow them.

Carroll has recently been released on licence after four months of a 14-month prison sentence for misconduct in a public office.

He told Manchester Evening News he now regrets pleading guilty to the charge, claiming he only did this as part of a deal to protect his police officer wife.

GMP Chief Constable Sir Peter Fahr has described Carroll’s fall from grace as a ‘personal tragedy’.

Now sober and clean, he has spoken of his struggles with ‘smackhead’ alter-ego Lee Taylor: ‘I was hallucinating, I got to the point where I was more comfortable being my alter-ego than I was being me.’

A GMP spokesman has stated they are aware of legal proceedings brought against them by Carroll and have chosen not to comment.